Dual Z motors, SKR Mini E3 2.0
I bought a dual z (HICTOP, no belt) and installation was easy but I problems syncing the two so the gantry only moves a short distance before grinding. I'm guessing a lot of the problem is mechanical so I'm going to tweak that. But BTT relevant:
- The hardware came with a jumper between the original z stepper connector and the new one. I've connected it that way. But the board also has I think two Z connectors (ZAM and ZBM) is it better to use those?
- Do I need to recompile custom Marlin? I see two relevant sections in configuration_adv.h:
- X_DUAL_STEPPER_DRIVERS. Set to two? What about the resulting conditional variables, I don't think Z_MULTI_ENDSTOPS is relevant, I'm using BTTouch as an endstop.
- What about "@section stepper motor current"? Do I need to increase that and which one and by how much?
Posted Aug 28, 2021, 7:05 PM UTC
212
The board only has a single stepper driver for Z, which the board splits to 2 plugs. You don't need to use the jumper cable, you can plug straight into the 2 board connectors.
But you still cannot have independent motor control. There are not dual stepper drivers.
Hopefully others can chime in on current. I'd guess maybe increase it by like 20% to start, to deal with the slight added mechanical drag?
Thanks, can I use the 3 way y jumper that came with it (two male, one female), should I just remove the original Creality wires?
Also what do drag issues look like? My gantry is tight so I think I need to manually adjust, but after that will it be slowness, or trouble at the ends of the axis?
I'd use whatever requires fewer connections, to reduce the risk of problems. It doesn't make a functional difference which wires you use.
Before my dual motor dual Z conversion, my Z axis moved fairly easily. I loosened the gantry wheels slightly when I did the conversion, since now it is properly supported on both sides. So it does not rely as much on the wheels being tight, to hold the gantry level.
If the gantry is loose when lowered, but tight when raised to almost the top, etc, then it would sound like your mechanical setup needs to be tweaked.
Yeah while dual z is nice to have in general, I got it because of gantry issues. I was able to get mine non-wobbly, there was still enough left right difference that I couldn't level the bed.
(edit: with single-Z, stock) I was able to level the bed OK, but didn't like the fact that, even with the wheels adjusted as best I could, there was still a bit of up/down play on the right-hand side.
The dual-Z has been a nice solution. But with dual motor drivers and BLTouch, mine self-levels the two sides before each print. If you're going to manually level the two sides, you might try adding anti-backlash nuts to both Z screws. I've found that between prints, my two sides will drift a bit. Like it will self-level before print 1, and when it checks itself again before print 2 (after the steppers turn off), it's not quite level. I'm guessing a Z screw shifts just slightly after the stepper turns off.
Anti-backlash nuts ought to help with that. Or I heard someone mention a Marlin feature (I think) that reduces the Z stepper current temporarily, and drives both sides all the way up until they hit the frame, to mechanically bring them to the same height. Then I think it raises the current again, drops Z, and continues the print process. If I understood the feature correctly, that might help make the two sides consistent before each print.